1. Field Of The Invention
The present invention relates to a flexible hose formed from a helically wound co-extruded strip having a reinforcing and interlocking rib of hardness generally greater and less flexible than its web connection.
2. Description Of The Prior Art And Background Considerations
While the present invention was originally conceived as being an all-plastic equivalent of solid or stranded wire-reinforced vinyl hose, it is to be understood that this original concept is adaptable to the general class of flexible hoses. Nevertheless, to provide a background to the present invention, it will be useful to discuss some aspects of its development.
As is well known in the art, a wire-reinforced vinyl hose comprises in general a hard rib of wire, with or without a plastic casing, which is surrounded by or connected to a relatively thin and/or flexible web. Such a hose is, by one conventional method, fabricated by winding the wire about a supporting mandrel, over which the web is placed such as by a shrink-fit, wrapping or a combination thereof. While such a construction forms a flexible and durable hose, certain drawbacks result therefrom. First, it is not possible to fabricate such a hose in continuously extended lengths because a mandrel is required for supporting the wire about which the web is placed. Thus, one limitation primarily relates to the length to which a mandrel can reasonably be made. Of course, mandrels can be made to any desired length, so long as there is proper space and support for the mandrel; however, the problem is one of reasonableness. The second limitation is one of cost. Wire has become very expensive and, as a result, such a hose becomes less competitive with other hoses. Secondary cost limitations are the requirement for two or three components comprising the wire, whether bare or plastic covered, and the web which must be placed thereover. A further cost is the increase in handling fabrication which is required.
Several efforts have been made to overcome the above problems as illustrated, for example, in U.S. Pat. Nos. 3,890,181 and 3,910,808. In the former patent, a strip of first plastic material is extruded along with a reinforcing element of a second plastic material. The strip is wound into a helix around a driven mandrel and bonded at adjacent turns together by pressure and heat or solvent. At the same time, the reinforcing element is wound about the helix of the first plastic material in spaced apart helical turns impressed into and partially embedded within the strip. While such a process is stated to permit the use of different plastic materials for achieving any desired hose characteristics, one difficulty is the ability to maintain definite and advantageous shapes, leading to distortion, as a result of assembly of the hose during the semi-molten condition of its component materials.
U.S. Pat. No. 3,910,808 describes a plastic strip having a longitudinal rib in which one edge of each convolution overlaps and is heat bonded to an edge of a preceding convolution, with the rib being on the exterior of the thus-formed tube. Since such a hose is formed of a single material, its rib strength is derived from the mass of material necessary to obtain the desired resistance to radial crush. Accordingly, one major problem is the cost resulting from the mass of material needed for the rib. It also is subject to similar assembly distortion problems as with the previously described hose.
In view of the above problems with the prior art, a different approach involved use of the profile shown in U.S. Pat. No. 3,255,780 in which its axially extending base planar leg was lengthened so as to obtain a configuration generally having the appearance of hose 11 shown herein in FIG. 1 of the attached drawings. In contradistinction to utilizing the flexibility of the loops required by U.S. Pat. No. 3,255,780, loops 12 of FIG. 1 were completely filled with bonding material 14 about both sides of inner radial leg 16 so as to form a helically extending solid and heavy rib 18. This heavy rib mass gave good resistance to radial crush exerted on hose 11 while elongated axially-extending base planar leg 19 was capable of flexing or bending to impart the entire hose with flexibility. Such a hose was in fact sold in 1973 (thus, it is acknowledged as prior art as having been "on sale" for more than one year prior to the filing hereof); however, because of cost problems due to the use of the relative large amount of plastic material required, it was not sufficiently competitive in the market.
Further prior art of interest, U.S. Pat. No. 3,199, 541 describes a flexible hose which is formed from a helically arranged elongated strip in which adjacent convolutions are interlocked by opposed mating male and female connecting elements on the strip. At least one of the male and female connecting elements is said to have a composite structural formation defined in part by the strip and in part by a resinous plastic material substantially stiffer than the strip material. The resinous plastic material is said to contribute to the crush resistance of the hose. Flexibility, however, is obtained from a radially extending leg using the same flexible loop concept described in above-mentioned U.S. Pat. No. 3,255,780.
Other prior art of interest herein includes a heavy section hose which the Assignee (Plastiflex Co.) hereof has sold for more than one year prior to the filing hereof under the trademark "Hi-Vac", which is an all plastic hose formed from two components. One component comprises an extruded thick and heavy web section of general W-shape with a bellow which imparts flexibility to the hose. Radially outwardly extending legs abut at adjacent convolutions of the W-shaped web section and are joined together by a U-shaped heavy rib which is bonded to the radial legs, and the radial legs themselves are bonded to one another. The radial legs are required in part for bonding purposes and for imparting resistance to radial crush, and in part for holding and handling of the web section during formation of the hose, without which the web section could not be readily convoluted. The web section is of generally softer material than the rib, which has a greater hardness to enhance the abrasion resistance and the hoop strength of the hose. Notwithstanding the softness of the web section, the bellow centrally formed therein is required to impart flexibility to the hose.
Since published material such as advertising sheets describing the "Hi-Vac" suction hose may not be generally available, copies are filed concurrently herewith and made a part of the file wrapper hereof. In addition, for convenience, copies of the above-identified patents are also filed herewith.
While such "Hi-Vac" hose functions very well for its intended purpose, its purpose is primarily for resisting radial crush forces exerted when internal pressures of the hose are reduced below that of atmosphere, i.e., partial or complete vacuum, and for heavy duty industrial use where, for example, it is required to resist the weight of trucks and trailers and to convey heavy sludge. One general limitation is similar to those described above in that the bonding of the two radial legs together as well as the rib bonded thereto produces a very heavy and massive rib and a hose of large external diameter as compared to its internal diameter. The result precludes the obtaining of a smaller outer to inner diameter. Another limitation of the hose is the requirement that its radially extending legs are needed for assembly of its components.
As a result of the above problems, it was necessary to investigate new approaches, from which the present invention arose.